Using UICollectionLayoutListConfiguration with storyboards - ios

Question

Can you use the new UICollectionLayoutListConfiguration API in iOS 14 with collection views in storyboards?
I have a UICollectionViewController in a storyboard, which I configure with a custom list layout below:
var config = UICollectionLayoutListConfiguration(appearance: .plain)
let layout = UICollectionViewCompositionalLayout.list(using: config)
collectionView.setCollectionViewLayout(layout, animated: false)
collectionView.dataSource = dataSource
(In storyboards collection views can only be set with flow or custom layouts)
This uses a standard diffable data source:
return UICollectionViewDiffableDataSource(collectionView: collectionView) { (collectionView, indexPath, item) in
guard let cell = collectionView.dequeueReusableCell(
withReuseIdentifier: "SomeCell",
for: indexPath
) as? SomeCell else {
fatalError("Couldn't dequeue cell \(reuseIdentifier)")
}
cell.setItem(item)
return cell
}
However I get some really weird behaviour, such as IBOutlets being nil when rotating the screen, despite everything working fine before rotation.
I've found no good way to debug what is going on here, the stack trace looks correct and the cell's class is initilised and this is running on the main thread.

Answer 1

I have replicated each and every step of your code and the end result is as expected for me.
Here's end result in portrait mode
Here's end result in landscape mode
What I intended to do was to show a list of numbers in the collection view, here are the necessary files for your reference:
The UICollectionViewController
import UIKit
private let reuseIdentifier = "SomeCell"
enum Section {
case main
}
class SampleCollectionViewController: UICollectionViewController {
var dataSource: UICollectionViewDiffableDataSource<Section, Int>!
override func viewDidLoad() {
super.viewDidLoad()
self.collectionView.setCollectionViewLayout(getLayout(), animated: false)
configureDataSource()
}
func getLayout() -> UICollectionViewCompositionalLayout {
let config = UICollectionLayoutListConfiguration(appearance: .plain)
let layout = UICollectionViewCompositionalLayout.list(using: config)
return layout
}
func configureDataSource() {
dataSource = UICollectionViewDiffableDataSource<Section, Int>(collectionView: self.collectionView, cellProvider: { (collectionView, indexPath, number) -> UICollectionViewListCell? in
guard let cell = collectionView.dequeueReusableCell(withReuseIdentifier: reuseIdentifier, for: indexPath) as? SomeCell else {
fatalError("Cannot create cell")
}
cell.label.text = number.description
return cell
})
var initialSnapshot = NSDiffableDataSourceSnapshot<Section, Int>()
initialSnapshot.appendSections([.main])
initialSnapshot.appendItems(Array(1...100), toSection: .main)
dataSource.apply(initialSnapshot, animatingDifferences: false)
}
}
The UICollectionViewListCell
import UIKit
class SomeCell: UICollectionViewListCell {
#IBOutlet weak var label: UILabel!
override func updateConstraints() {
super.updateConstraints()
label.textColor = .blue
}
}
The storyboard setup:
I did all this following standard steps nothing fancy here
Important Note: One potential place where I found your implementation different was that you have dequeued a cell withReuseIdentifier as "SomeCell" but the cell class you have shown throwing error is TextCell if you could provide more specifics on the same then it would be helpful to narrow down the error you are facing.

Answer 2

Here is simplified demo. Much of based on somehow replicated your code.
Tested with Xcode 12 / iOS 14
struct SomeItem: Hashable {
let id = UUID()
var value: String
}
class SomeCell: UICollectionViewCell {
#IBOutlet weak var label: UILabel!
var item: SomeItem!
func setItem(_ item: SomeItem) {
self.item = item
label.text = item.value
}
override func awakeFromNib() { // called when all outlets connected
super.awakeFromNib()
label.textColor = .blue
}
}
class ViewController: UICollectionViewController {
override func viewDidLoad() {
super.viewDidLoad()
let config = UICollectionLayoutListConfiguration(appearance: .plain)
let layout = UICollectionViewCompositionalLayout.list(using: config)
collectionView.setCollectionViewLayout(layout, animated: false)
collectionView.dataSource = dataSource
}
lazy var dataSource = {
UICollectionViewDiffableDataSource<Int, SomeItem>(collectionView: self.collectionView) { (collectionView, indexPath, item) in
guard let cell = collectionView.dequeueReusableCell(
withReuseIdentifier: "SomeCell",
for: indexPath
) as? SomeCell else {
fatalError("Couldn't dequeue cell")
}
cell.setItem(item)
return cell
}
}()
override func viewWillAppear(_ animated: Bool) {
super.viewWillAppear(animated)
var snapshot = NSDiffableDataSourceSnapshot<Int, SomeItem>()
snapshot.appendSections([0])
snapshot.appendItems([SomeItem(value: "Jan"), SomeItem(value: "Fab"), SomeItem(value: "Mar")])
dataSource.apply(snapshot)
}
}
Nothing special in storyboard - only applied custom classes for view controller and cell (label is centred for simplicity) and made custom collection view layout: